Combating unwanted vegetation with 1,3,4-thiadiazole-2-sulfonamides

ABSTRACT

A class of 5-ureido and thioureido-1,3,4-thiadiazole-2-sulfonamides bearing various substituents on both sulfonamide and ureido nitrogen atoms is employed to combat unwanted vegetation both pre- and post-emergently.

DESCRIPTION OF THE INVENTION

A new class of highly phytotoxic substances has been discovered which may be applied to the locus of unwanted vegetation to effect control, either pre- or post-emergently. Effective compounds have the structural formula ##STR1## in which R¹ and R² are selected from hydrogen, lower cycloalkyl, lower alkyl, alkoxy, cyanoalkyl, aralkyl, alkoxyalkyl, alkylaminoalkyl, lower alkenyl and lower alkynyl substituents and heterocyclic structures in which R¹ and R² are together alkylene or oxyalkylene with two to five carbon atoms, R³ is hydrogen, methyl or ethyl, R⁴ is hydrogen or lower alkyl, R⁵ is selected from lower alkyl, lower alkenyl and lower cycloalkyl substituents and X is oxygen or sulfur. In the preferred embodiment of the method a phytotoxic agricultural composition is prepared for use, comprising an effective amount of a compound as defined above, in combination with a major amount of an efficient organic solvent and a minor amount of a surface active agent, sufficient to disperse the composition in water. The most useful efficient solvents generally are mixtures of industrial solvents, usually selected from hydrocarbon, ketone and ester types, mixtures being more economical and efficient than individual substances. Both solvents and surface active agents are conveniently selected from those which are approved for agricultural use by the proper regulating agencies. Specific solvents which are useful in the preparation of the preferred type of agricultural compositions are toluene, xylene, isophorone, cyclohexanone, mesityl oxide and ethyl acetate. Blends of anionic and nonionic surfactants have proved to be particularly desirable as dispersing agents.

Specific compounds which are illustrative of the class of herbicides are listed in Table 1.

                                      TABLE I                                      __________________________________________________________________________      ##STR2##                                                                      __________________________________________________________________________     COMPOUND                                                                       NO.    R.sup.1  R.sup.2    R.sup.3                                                                           R.sup.4                                                                           R.sup.5   M.P.   X                            __________________________________________________________________________     1      C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                           CH.sub.3                                                                          H  CH.sub.3  208.0-209.5                                                                           O                            2      H        CH.sub.3   H  H  CH.sub.3  227-8  O                            3      H        C.sub.2 H.sub.5                                                                           H  H  CH.sub.3  199-200                                                                               O                            4      H        iC.sub.3 H.sub.7                                                                          H  H  CH.sub.3  183-6  O                            5      H        nC.sub.4 H.sub.9                                                                          H  H  CH.sub.3  183-5  O                            6      H        CH.sub.2 CHCH.sub.2                                                                       H  H  CH.sub.3  193-194.5                                                                             O                            7      H        tC.sub.4 H.sub.9                                                                          H  H  CH.sub.3  245-6 (dec)                                                                           O                            8      H        cycloC.sub.3 H.sub.5                                                                      H  H  CH.sub.3  181-3  O                            9      H        C.sub.6 H.sub.5 CH.sub.2                                                                  H  H  CH.sub.3  175-8  O                            10     C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                           H  H  CH.sub.3  168-9  O                            11     nC.sub.3 H.sub.7                                                                        nC.sub.3 H.sub.7                                                                          H  H  CH.sub.3  144-6  O                            12     nC.sub.4 H.sub.9                                                                        nC.sub.4 H.sub.9                                                                          H  H  CH.sub.3  146-8  O                            13     isoC.sub.4 H.sub.9                                                                      isoC.sub.4 H.sub.9                                                                        H  H  CH.sub.3  174-5  O                            14     C.sub.2 H.sub.5                                                                         nC.sub.4 H.sub.9                                                                          H  H  CH.sub.3  177-9  O                            15     (R.sup.1,R.sup.2 =CH.sub.2 CH.sub.2 OCH.sub.2 CH.sub.2)                                            H  H  CH.sub.3  229-3  O                            16     iC.sub.3 H.sub.7                                                                        C.sub.6 H.sub.5 CH.sub.2                                                                  H  H  CH.sub.3  165-8  O                            17     H        C.sub.6 H.sub.5                                                                           H  H  CH.sub.3  189-90 O                            18     C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                           CH.sub.3                                                                          H  C.sub.2 H.sub.5                                                                          178-80 O                            19     C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                           CH.sub.3                                                                          H  iC.sub.3 H.sub.7                                                                         84.0-86.5                                                                             O                            20     C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                           CH.sub.3                                                                          H  nC.sub.3 H.sub.7                                                                         115-6  O                            21     C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                           CH.sub.3                                                                          H  C.sub.6 H.sub.5                                                                          126-8  O                            22     C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                           CH.sub.3                                                                          H  CH.sub.2CHCH.sub.2                                                                       107-8  O                            23     C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                           CH.sub.3                                                                          H  CH.sub.3  130-1  S                            24     H        H          H  H  CH.sub.3  >310   O                            25     CH.sub.2 CHCH.sub.2 CH.sub.2 CHCH.sub.2                                                            H  H  CH.sub.3  134-5  O                            26     H                                                                                        ##STR3##  H  H  CH.sub.3  179-82 O                            27                                                                                     ##STR4##                                                                                ##STR5##  H  H  CH.sub.3  191-3  O                            28     H        nC.sub.3 H.sub.7                                                                          H  H  CH.sub.3  169-71 O                            29     CH.sub.3 CH.sub.2 CH.sub.2 CN                                                                      H  H  CH.sub.3  168-71 O                            30     C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                           CH.sub.3                                                                          H  cycloC.sub.6 H.sub.11                                                                    114-115.5                                                                             O                            31     C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                           CH.sub.3                                                                          CH.sub.3                                                                          CH.sub.3  63-5   O                            32     H        iC.sub.3 H.sub.7                                                                          CH.sub.3                                                                          H  CH.sub.3  197-9  O                            33     CH.sub.3 CH.sub.3   H  H  CH.sub.3  193-6  O                            34     H        CH.sub.3   CH.sub.3                                                                          H  CH.sub.3  158-60 O                            35     H        CH.sub.2 CHCH.sub.2                                                                       CH.sub.3                                                                          H  CH.sub.3  145-7  O                            36     H        cyclo C.sub.3 H.sub.5                                                                     CH.sub.3                                                                          H  CH.sub.3  193-5  O                            37     CH.sub.3 CH.sub.3   CH.sub.3                                                                          H  CH.sub.3  211-14 O                            38     H        CH.sub.2 C.sub.6 H.sub.5                                                                  CH.sub.3                                                                          H  CH.sub.3  oil    O                            39     CH.sub.2 CHCH.sub.2                                                                     CH.sub.2 CHCH.sub.2                                                                       CH.sub.3                                                                          H  CH.sub.3  109-11 O                            40     CH.sub.3 CH.sub.3   C.sub.2 H.sub.5                                                                   H  CH.sub.3  145-148.5                                                                             O                            41     H                                                                                        ##STR6##  CH.sub.3                                                                          H  CH.sub.3  123-4  O                            42     CH.sub.3 CH.sub.3   CH.sub.3                                                                          CH.sub.3                                                                          CH.sub.3  89-91  O                            43     H        cyclo C.sub.3 H.sub.5                                                                     C.sub.2 H.sub.5                                                                   H  CH.sub.2 CHCH.sub.2                                                                      155-7  O                            44     CH.sub.3 CH.sub.3   C.sub.2 H.sub.5                                                                   CH.sub.3                                                                          CH.sub.3  71-2   O                            45     H        cyclo C.sub.3 H.sub.5                                                                     C.sub.2 H.sub.5                                                                   H  CH.sub.3  83.5-84.5                                                                             O                            46     H        C.sub.18 H.sub.37                                                                         CH.sub.3                                                                          H  CH.sub.3  118-130                                                                               O                            47     H        CH.sub.2 CH.sub.2 OH                                                                      CH.sub.3                                                                          H  CH.sub.3  187-9  O                            48     (R.sup.1,R.sup.2 = CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2)                                   CH.sub.3                                                                          H  CH.sub.3  220-4  O                            49     H        CH.sub.2 CH.sub.2 CH.sub.2 OCH.sub.3                                                      CH.sub.3                                                                          H  CH.sub.3  91-3   O                            50     H        CH.sub.2 CH.sub.2 N(C.sub.2 H.sub.5).sub.2                                                CH.sub.3                                                                          H  CH.sub.3  89-92  O                            __________________________________________________________________________

Several general methods may be used to prepare the compounds listed in Table I.

For all those (I) where R³ =H (compound Nos. 2-17 and 24-29) and some where R³ =CH₃ (compound Nos. 32- 39, 41 and 46- 50) the route shown in Scheme A was used, starting with the known 2-amino-5-mercapto-1,3,4-thiadiazoles (IVa and IVb) ##STR7##

In the reaction of IVa and IVb with methyl isocyanate using either benzene or dioxane as solvent, the product obtained did not have structure V (a or b), but was an isomer or mixture of isomers. In the case of the product for IVa, conversion to Va could be accomplished by either recrystallizing from ethanol or methanol or by warming slightly in dimethyl sulfoxide solution. While these methods were ineffective when R³ =CH₃, Vb was obtained in good yield by heating the initial IVb methyl isocyanate reaction product with triethylamine.

The structures of the isomeric precursors to Va and Vb have not been determined but the more likely possibilities are VII, VIII and IX. ##STR8## Chlorination of a suspension of Va or Vb in dilute hydrochloric acid gave, in good yield, the sulfonyl chloride (VI) which reacted smoothly with ammonia and amines to give the sulfonamides.

The preparation of the remainder of those (I) where R³ =CH₃ or C₂ H₅ was according to Scheme B. ##STR9##

Preparation of N-Methyl-N'-(5-mercapto-1,3,4-thiadiazol-2-yl)urea ##STR10## To a suspension of 10.5 g of 2-amino-5-mercapto-1,3,4-thiadiazole in 100 ml of benzene is added 4.5 g of methyl isocyanate and the mixture is stirred overnight at room temperature. The solid is collected by filtration, dried and dissolved in the minimum quantity of dimethyl sulfoxide by warming slightly. Dilution of this solution with water gives 13.0 g of N-methyl-N'-(5-mercapto-1,3,4-thiadiazol-2-yl)urea. A sample recrystallized from ethanol melted at 230°-232° with decomposition. Preparation of N-Methyl-N'-(5-chlorosulfonyl-1,3,4-thiadiazol-2-yl)urea ##STR11## Chlorine gas is bubbled rapidly at 0°-7° through a stirred suspension of 8.0 g. of N-methyl-N'-(5-mercapto-1,3,4-thiadiazol-2-yl)urea in 200 ml. of 10% hydrochloric acid. After 1- 2 hours, the mixture appears saturated with excess chlorine and the solid present is collected by filtration and washed with water to give 10.5 g of N-Methyl-N'-(5-chlorosulfonyl-1,3,4-thiadiazol-2-yl)urea m.p. 155° (dec.). Preparation of N,N'-Dimethyl-N'-(5-Mercapto-1,3,4-thiadiazol-2-yl)urea ##STR12##

To a stirred slurry of 126 g of 2-methylamino-5-mercapto-1,3,4-thiadiazole in 525 ml of dioxane containing a few drops of triethylamine is added 49 g of methyl isocyanate. After stirring two hours at room temperature, the solid is collected by filtration and washed with hexane giving 165 g, melting at 162°-3°. This product is heated on the steam bath 11/2 -2 hours with 250 ml of triethylamine, during which time the initial solid is converted to a heavy amber oil. The supernatent liquid is decanted and the oil is dissolved in water and neutralized with dilute hydrochloric acid to pH 2-3. The precipitated solid is collected and washed with water and air dried, giving 132 g of N,N'-dimethyl-N'-(5-mercapto-1,3,4-thiadiazol-2-yl)urea, m.p. 230° (dec.).

Preparation of N,N'-Dimethyl-N'-(5-chlorosulfonyl-1,3,4-thiadiazol-2-yl)urea ##STR13##

Chlorine gas is bubbled rapidly through a suspension of 20 g of N,N'-dimethyl-N'-(5-mercapto-1,3,4-thiadiazol-2-yl)urea in 300 ml of 10% hydrochloric acid. When the mixture is saturated with chlorine, the solid is filtered, washed with water and air dried to give 22.8 g of N,N'-dimethyl-N'-(5-chlorosulfonyl-1,3,4-thiadiazol-2-yl)urea, m.p. 95° (dec.).

Preparation of 2-(N'-Methylcarbamido) or (N,N'-Dimethylcarbamido)-1,3,4-thiadiazole-5-sulfonamides ##STR14##

The sulfonamides (Nos. 2-17, 24-29, 32-39 and 41) listed in Table I, where R³ =H or CH₃ were prepared by a general method illustrated by the following procedure

To a stirred and cooled solution of 5.9 g of diisobutylamine in 30 ml of dioxane is added rapidly, in small portions, 5.9 g of N-methyl-N'-(5-chlorosulfonyl)-1,3,4-thiadiazol-2-yl)urea. After stirring one hour in the ice bath, the slurry is diluted 2- 4 fold with water, giving 6.7 g of 2-(N-methyl-carbamido)-1,3,4-thiadiazole-5-N,N-diisobutylsulfonamide, m.p. 174°-5° .

Those sulfonamides (Nos. 1, 18-23, 30, 31, 40 and 43-45) listed in Table I in which R³ is alkyl were prepared by general methods illustrated by the following procedures

Preparation of 2-(N'-methylacetamido)-1,3,4-thiadiazole-5-sulfonamides Method A

Diethylamine (36.5 g, 0.5 mol) in 50 ml acetone was chilled in an ice-water bath. To the stirred solution was added portionwise over a 30 min. period 2-(N'-methylacetamido)-1,3,4-thiadiazole-5-sulfonyl chloride (25.6 g 0.1 mol). After an additional 15 min. of stirring, the thick white suspension was poured onto 400 ml of ice-water containing 100 ml 10% HCl. The white solid was isolated by filtration and after washing several times with water was air dried affording 28 g (96%) of product, m.p. 148°-50°.

Method B

Procedure as in A except that p-dioxane was used in place of acetone. Reactants were used in the ratio of 30mmol of sulfonyl chloride: 60 mmol of amine: 30 ml of dioxane. The product was removed by filtration and a second crop obtained by diluting the filtrate with water affording a 91% yield, m.p. 152.5°-3.0°.

Preparation of 2-N'-Methylamino-1,3,4-thiadiazole-5-N,N-diethylsulfonamide

A suspension of 2-(N'-methylacetamido-1,3,4-thiadiazole-5-N,N-diethylsulfonamide (23g, 0.8 mol) in 1 liter of 10% NaOH with sufficient ethanol to partially effect solution was stirred overnight at room temperature. Ice was added and the resulting white solid removed by filtration. Washing several times with cold water and drying on filter afforded 16 g (80%) of product, m.p. 129.0°-130.0°. Thin layer chromatography (Brinkmann silica gel: CHCl₃ with 10% acetone) indicated reaction complete after 4 hours.

Preparation of 5-(1,3-Dimethylureido)-N,N-diethyl-1,3,4-thiadiazole-2-sulfonamide

To a stirred suspension of 2-N'-methylamino-1,3,4-thiadiazole-5-N,N-diethylsulfonamide (5 g, 20 mmol) in 30 ml p-dioxane was added dropwise at room temperature methyl isocyanate (1.2 g, 20 mmol). Stirred 1.5 hr and product removed by filtration affording 4.2 g (69%) product, m.p. 208.0°-9.5°. (Abs. EtOH)

Combating Unwanted Vegetation

The novel herbicides are effective when used both post- and pre-emergently. There is described below an illustrative procedure for herbicidal use of the compounds under controlled conditions in the greenhouse so as to obtain data on phytotoxic activity and selectivity.

(1) Post-Emergent Use

An aqueous dispersion of each active compound was prepared by combining 0.4 gram of the compound with about 4 ml of a solvent-emulsifier mixture (3 parts of a commercial polyoxyethylated vegetable oil emulsifier, one part xylene, one part kerosene) and then adding water, with stirring, to a final volume of 40 ml.

The species of plants on which each compound was to be tested were planted in four-inch pots in a greenhouse. Ten to eighteen days after emergence of the plants, three pots of each species were sprayed with an aqueous dispersion of the active compound prepared as described above, at a rate of 5 lb of active compound per acre and at a spray volume of 60 gallons per acre. Approximately one week after the spray application the plants were observed and the results rated according to the following schedule.

DEGREE OF EFFECT

0 = no effect

1 = slight effect

2 = moderate effect

3 = severe effect

4 = maximum effect (all plants died.)

The same rating schedule was employed to judge pre-emergent results obtained according to the procedure below.

(2) Pre-Emergent Use

A solution of each active compound was prepared by dissolving 290 mg of the compound to be tested in 200 ml of acetone. Disposable expanded polystyrene trays about 21/2 inches deep and about one square foot in area were prepared and seeded with the acetone solution at the rate of 10 lb of active chemical per acre of sprayed area and were then covered with about 1/4 inch of soil. One group of trays, which had been seeded with alfalfa, brome, flax, oats, radishes and sugar beets were held at 75° F. day temperature; another set of trays seeded with corn, coxcomb, cotton, crabgrass, millet and soybeans was held at 85° F. Twenty-one days after seeding and treatment the plantings were examined and herbicidal effect was rated according to the above schedule.

Both post-emergent and pre-emergent results are set forth in Table II.

                                      TABLE II                                     __________________________________________________________________________     COMPOUND                                                                              USE                                                                     NO.    TYPE                                                                               Crabgrass                                                                           Coxcomb                                                                             Brome                                                                              Millet                                                                             Alfalfa                                                                            Oats                                                                              Radish                                                                             Sugar Beet                                                                           Tomato                           __________________________________________________________________________      1     Post              4   4   4  4   4     4                                       Pre 4    4    4   4   --  -- 4   4                                       2     Post              4   4   4  4   4     4                                       Pre 4    4    4   4   --  -- 4   4                                       3     Post              4   4   4  4   4     4                                       Pre 4    4    4   4   --  -- 4   4                                       4     Post              4   4   4  4   4     4                                       Pre 4    4    4   4   --  -- 4   4                                       5     Post              3   4   3  4   4     4                                       Pre 2    3    3   3   --  -- 4   4                                       6     Post              4   4   4  4   4     4                                       Pre 3    3    4   4   --  -- 4   4                                       7     Post              0   4   0  2   4     3                                       Pre 2    4    3   2   --  -- 4   4                                       8     Post              4   4   4  4   4     4                                       Pre 3    4    4   4          4   4                                       9     Post              3   4   2  4   4     4                                       Pre 1    2    2   1          2   2                                      10     Post              4   4   4  4   4     4                                       Pre 4    4    4   4   --  -- 4   4                                      11     Post              3   4   2  4   4     4                                       Pre 2    4    4   3   --  -- 4   4                                      12     Post              1   4   1  4   4     4                                       Pre 0    2    0   0   --  -- 1   2                                      13     Post              3   4   1  4   4     4                                       Pre 1    4    2   1          2   4                                      14     Post              4   4   3  4   4     4                                       Pre 1    3    4   3          4   4                                      15     Post              4   4   4  4   4     4                                       Pre 3    4    4   4          4   4                                      16     Post              3   4   1  4   4     4                                       Pre 1    3    4   0          4   4                                      17     Post              0   1   0  1   3     2                                       Pre 0    3    0   1          1   3                                      18     Post              3   4   3  4   4     4                                       Pre 4    4    4   4          4   4                                      19     Post              1   3   2  4   4     4                                       Pre 2    4    4   4          4   4                                      20     Post              1   4   1  3   4     3                                       Pre 1    4    3   3          4   4                                      21     Post              0   0   0  0   0     0                                       Pre 1    3    1   1          1   1                                      22     Post              4   4   4  4   4     4                                       Pre 2    4    4   4          4   4                                      23     Post              1   3   1  4   4     3                                       Pre 2    4    3   3          4   4                                      24     Post              0   1   0  1   3     4                                       Pre 0    0    1   0          0   1                                      25     Post              4   4   3  4   4     4                                       Pre 3    4    4   4          4   4                                      26     Post              4   4   4  4   4     4                                       Pre 3    4    4   4          4   4     4                                27     Post              4   4   1  4   4     4                                       Pre 3    4    4   4          4   4                                      28     Post              4   4   4  4   4     4                                       Pre 4    4    4   4          4   4                                      29     Post              4   4   3  4   4     4                                       Pre 4    4    4   4          4   4                                      30     Post              1   0   0  2   1     1                                       Pre 0    1    0   0          1   1                                      31     Post              4   4   4  4   4     4                                       Pre 4    4    4   4          4   4                                      32     Post              4   4   4  4   4     4                                       Pre 3    4    4   4          4   4                                      33     Post              4   4   4  4   4     4                                       Pre 3    4    4   4          4   4                                      34     Post              4   4   4  4   4     4                                       Pre 3    4    4   4          4   4                                      35     Post              4   4   4  4   4     4                                       Pre 3    4    4   4          4   4                                      36     Post              4   4   4  4   4     4                                       Pre 2    4    2   3          2   4                                      37     Post              4   4   4  4   4     4                                       Pre 3    4    4   4          4   4                                      38     Post              4   4   3  4   4     4                                       Pre                                                                     39     Post              4   4   4  4   4     4                                       Pre                                                                     40     Post              4   4   4  4   4     4                                       Pre                                                                     __________________________________________________________________________

In a further test of both pre and post-emergent use of illustrative compounds, twenty-four species of plants were treated. Although there were in several instances fairly severe effects on soybeans, peanuts, cotton, corn and grain sorghum some of the compounds killed a number of plant species in the presence of these crop plants. Results are presented in Table III. The ratings were all made according to the schedule disclosed above.

                  TABLE III                                                        ______________________________________                                         COMPOUND NO. 1                                                                 MODE OF      PRE           POST                                                APPLICATION  3 lb/A   1 lb/A   3 lb/A 1 lb/A                                   ______________________________________                                         Plant Species                                                                  Cocklebur    4        4        *4     *4                                       Lambsquarter 4        4        4      4                                        Morning Glory                                                                               4        4        4      2                                        Pigweed      4        4        4      4                                        Wild Buckwheat                                                                              4        4        4      4                                        Wild Mustard 4        4        4      4                                        Barnyard Grass                                                                              4        4        4      3                                        Crabgrass    4        4        4      3                                        Downy Brome  4        3        3      0                                        Giant Foxtail                                                                               4        4        4      1                                        Green Foxtail                                                                               4        4        4      2                                        Nutsedge     1        0        3      0                                        Shattercane  4        4        4      1                                        Wild Oats    4        4        4      1                                        Alfalfa      3        1        4      0                                        Cotton       4        3        4      4                                        Peanut       2        0        1      0                                        Soybean      4        4        4      3                                        Sugar Beets  4        4        4      3                                        Tomato       4        4        4      4                                        Corn         4        4        2      1                                        Grain Sorghum                                                                               4        4        3      0                                        Rice         4        4        4      1                                        Wheat        4        4        4      1                                        COMPOUND NO. 2                                                                 Plant Species                                                                  Cocklebur    0        0        --     --                                       Lambsquarter 4        1        4      4                                        Morning Glory                                                                               0        0        1      1                                        Pigweed      4        3        4      4                                        Wild Buckwheat                                                                              2        0        4      4                                        Wild Mustard 4        1        4      4                                        Barnyard Grass                                                                              4        3        4      4                                        Crabgrass    4        3        4      4                                        Downy Brome  3        0        3      1                                        Giant Foxtail                                                                               4        2        4      4                                        Green Foxtail                                                                               4        2        4      4                                        Nutsedge     0        0        0      0                                        Shattercane  4        3        4      3                                        Wild Oats    3        1        4      4                                        Alfalfa      3        1        4      4                                        Cotton       0        0        4      4                                        Peanut       0        0        2      1                                        Soybean      0        0        4      2                                        Sugar Beets  1        0        4      4                                        Tomato       4        1        4      4                                        Corn         3        2        2      1                                        Grain Sorghum                                                                               4        2        4      3                                        Rice         4        3        4      3                                        Wheat        4        3        4      4                                        COMPOUND NO. 3                                                                 Plant Species                                                                  Cocklebur    0        0        *4     *4                                       Lambsquarter 4        4        4      4                                        Morning Glory                                                                               0        0        2      1                                        Pigweed      4        4        4      4                                        Wild Buckwheat                                                                              0        0        4      4                                        Wild Mustard 4        1        4      4                                        Barnyard Grass                                                                              4        4        4      4                                        Crabgrass    4        4        4      4                                        Downy Brome  4        3        4      2                                        Giant Foxtail                                                                               4        4        4      3                                        Green Foxtail                                                                               4        4        4      4                                        Nutsedge     0        0        0      0                                        Shattercane  4        3        3      3                                        Wild Oats    4        4        4      4                                        Alfalfa      3        1        4      4                                        Cotton       0        0        4      3                                        Peanut       0        0        1      0                                        Soybean      0        0        3      3                                        Sugar Beets  4        4        4      4                                        Tomato       4        3        4      4                                        Corn         4        2        2      1                                        Grain Sorghum                                                                               4        3        4      2                                        Rice         4        4        3      1                                        Wheat        4        4        4      3                                        COMPOUND NO. 4                                                                 Plant Species                                                                  Cocklebur    0        0        *4     *4                                       Lambsquarter 4        4        4      4                                        Morning Glory                                                                               0        0        3      1                                        Pigweed      4        4        4      4                                        Wild Buckwheat                                                                              0        0        4      4                                        Wild Mustard 1        0        4      4                                        Barnyard Grass                                                                              3        2        3      2                                        Crabgrass    4        3        4      3                                        Downy Brome  4        3        3      1                                        Giant Foxtail                                                                               4        2        4      2                                        Green Foxtail                                                                               2        0        3      1                                        Nutsedge     0        0        0      0                                        Shattercane  3        0        1      0                                        Wild Oats    4        1        3      0                                        Alfalfa      1        0        4      2                                        Cotton       0        0        3      0                                        Peanut       0        0        1      1                                        Soybean      2        0        4      2                                        Sugar Beets  4        2        4      4                                        Tomato       4        0        4      4                                        Corn         2        0        2      0                                        Grain Sorghum                                                                               3        0        1      0                                        Rice         3        2        3      1                                        Wheat        4        2        2      0                                        COMPOUND NO. 5                                                                 Plant Species                                                                  Cocklebur    0        0        *3     *1                                       Lambsquarter 4        4        4      4                                        Morning Glory                                                                               0        0        2      1                                        Pigweed      4        4        4      4                                        Wild Buckwheat                                                                              1        0        4      3                                        Wild Mustard 4        0        4      4                                        Barnyard Grass                                                                              3        2        3      3                                        Crabgrass    3        3        4      3                                        Downy Brome  3        1        2      1                                        Giant Foxtail                                                                               3        2        3      2                                        Green Foxtail                                                                               2        1        4      2                                        Nutsedge     0        0        0      0                                        Shattercane  1        0        2      0                                        Wild Oats    3        2        3      1                                        Alfalfa      1        0        4      3                                        Cotton       0        0        3      0                                        Peanut       0        0        1      0                                        Soybean      1        0        3      3                                        Sugar Beets  4        1        4      3                                        Tomato       4        0        4      4                                        Corn         1        0        2      0                                        Grain Sorghum                                                                               1        0        2      0                                        Rice         3        2        2      1                                        Wheat        4        3        2      1                                        COMPOUND NO. 6                                                                 Plant Species                                                                  Cocklebur    0        0        *4     *4                                       Lambsquarter 4        4        4      4                                        Morning Glory                                                                               0        0        1      1                                        Pigweed      4        4        4      4                                        Wild Buckwheat                                                                              2        1        4      4                                        Wild Mustard 3        0        4      4                                        Barnyard Grass                                                                              4        3        4      1                                        Crabgrass    4        3        4      3                                        Downy Brome  4        3        3      1                                        Giant Foxtail                                                                               4        3        4      2                                        Green Foxtail                                                                               3        1        4      1                                        Nutsedge     0        0        0      0                                        Shattercane  3        1        2      0                                        Wild Oats    4        2        3      1                                        Alfalfa      1        0        3      2                                        Cotton       0        0        3      1                                        Peanut       0        0        1      0                                        Soybean      2        0        2      2                                        Sugar Beets  4        1        4      3                                        Tomato       4        3        4      4                                        Corn         4        1        2      1                                        Grain Sorghum                                                                               3        1        2      0                                        Rice         4        3        3      1                                        Wheat        4        4        3      1                                        COMPOUND NO. 7                                                                 Plant Species                                                                  Cocklebur    0        0        *0     *0                                       Lambsquarter 3        1        1      0                                        Morning Glory                                                                               0        0        0      0                                        Pigweed      4        2        1      0                                        Wild Buckwheat                                                                              0        0        1      0                                        Wild Mustard 0        0        2      0                                        Barnyard Grass                                                                              2        0        0      0                                        Crabgrass    3        0        0      0                                        Downy Brome  1        0        0      0                                        Giant Foxtail                                                                               2        0        0      0                                        Green Foxtail                                                                               1        0        0      0                                        Nutsedge     0        0        0      0                                        Shattercane  0        0        0      0                                        Wild Oats    0        0        0      0                                        Alfalfa      0        0        0      0                                        Cotton       0        0        0      0                                        Peanut       0        0        0      0                                        Soybean      0        0        1      1                                        Sugar Beets  4        0        2      1                                        Tomato       1        1        2      1                                        Corn         0        0        0      0                                        Grain Sorghum                                                                               0        0        0      0                                        Rice         1        0        0      0                                        Wheat        1        0        0      0                                        COMPOUND NO. 10                                                                Plant Species                                                                  Cocklebur    0        0        4      4                                        Lambsquarter 4        3        4      4                                        Morning Glory                                                                               0        0        3      2                                        Pigweed      4        4        4      4                                        Wild Buckwheat                                                                              1        0        4      4                                        Wild Mustard 4        4        4      4                                        Barnyard Grass                                                                              4        4        4      3                                        Crabgrass    4        3        4      4                                        Downy Brome  1        0        3      2                                        Giant Foxtail                                                                               4        2        4      4                                        Green Foxtail                                                                               4        4        4      4                                        Nutsedge     0        0        0      0                                        Shattercane  4        4        4      3                                        Wild Oats    3        0        4      3                                        Alfalfa      4        2        4      4                                        Cotton       1        0        4      4                                        Peanut       0        0        2      1                                        Soybean      1        0        4      4                                        Sugar Beets  4        3        4      4                                        Tomato       4        1        4      4                                        Corn         2        1        1      1                                        Grain Sorghum                                                                               4        3        4      2                                        Rice         3        3        4      2                                        Wheat        4        1        4      3                                        COMPOUND NO. 11                                                                Plant Species                                                                  Cocklebur    0        0        *2     *0                                       Lambsquarter 4        2        4      4                                        Morning Glory                                                                               0        0        1      0                                        Pigweed      4        4        4      4                                        Wild Buckwheat                                                                              0        0        4      4                                        Wild Mustard 0        0        4      4                                        Barnyard Grass                                                                              0        0        2      1                                        Crabgrass    1        0        2      1                                        Downy Brome  0        0        1      0                                        Giant Foxtail                                                                               0        0        2      1                                        Green Foxtail                                                                               0        0        1      0                                        Nutsedge     0        0        0      0                                        Shattercane  0        0        0      0                                        Wild Oats    1        0        1      0                                        Alfalfa      0        0        4      3                                        Cotton       0        0        3      3                                        Peanut       0        0        1      0                                        Soybean      0        0        4      1                                        Sugar Beets  1        0        4      4                                        Tomato       0        0        4      4                                        Corn         0        0        0      0                                        Grain Sorghum                                                                               0        0        0      0                                        Rice         2        0        1      0                                        Wheat        3        0        1      0                                        COMPOUND NO. 12                                                                Plant Species                                                                  Cocklebur                      *1     *0                                       Lambsquarter                   2      1                                        Morning Glory                  1      0                                        Pigweed                        1      1                                        Wild Buckwheat                 4      4                                        Wild Mustard                   4      4                                        Barnyard Grass                 0      0                                        Crabgrass                      2      0                                        Downy Brome                    2      0                                        Giant Foxtail                  2      0                                        Green Foxtail                  0      0                                        Nutsedge                       0      0                                        Shattercane                    0      0                                        Wild Oats                      0      0                                        Alfalfa                        2      1                                        Cotton                         4      1                                        Peanut                         1      0                                        Soybean                        1      1                                        Sugar Beets                    4      4                                        Tomato                         4      2                                        Corn                           0      0                                        Grain Sorghum                  0      0                                        Rice                           1      0                                        Wheat                          0      0                                        ______________________________________                                          0 = No injury                                                                  *Sunflower used in place of Cocklebur                                          4 = Complete Kill                                                              -- = No plants                                                            

We claim:
 1. The method of combating unwanted vegetation comprising applying to the locus of the unwanted vegetation an effective amount of 5-(1,3,3-trimethylureido)-N,N-dimethyl-1,3,4-thiadiazole-2-sulfonamide. 